Rocess for treating mineral oils



' Patented Mar- 7, 1939 e Z U'NlTEiD STATES PATENT OFFICE-- I.

PROCESS FOR. TREATING MINERAL OILS Wilbert B. McCluer and Merrell R.'Fenske, State College, 'Pa., assignor's to'Pennsylvania Petroleum Research Corporation, a corporation of Pennsylvania No Drawing. Application December 26, 1933,

v Serial No. 704,052

I 4 Claims. (Cl; 196-13) This invention pertains generally to the sepof oil. This feature follows directly from the aration of materiais into components and perfact that a large number of fractions can be obtains particularly to the separation of mineral tained from a given oil. Since both the viscosity oils into parts or fractions having different charand quality of the diiierent fractions vary, it is acteristicsj possible to produce oils of practically any grade 5 In accordance with this invention crude petroand quality by blending the various fractions in leum or products, thereof and particularly lubrithe desired proportions. cating oils are separated into various components Fractional precipitation is more eflicient than by first dissolving the material to be treated in simple single stage extraction. The increased a suitable solvent and then fractionally precipiefiiciency may be explained as follows: In single 10 tating the dissolved oil from said solvent. stage extraction or precipitation, a relatively large In a simple extraction process of the prior art,' percent of highly paraflinic materials must be equilibrium between the dissolved and undissolved present in the solvent layer at all times in order oil may be approached from either the low temto maintain equilibrium between the dissolved perature or high temperature side. If equilibriand undissolved oil and the amount of these 15 um is approached from the low temperature (or highly p'araflinic dissolved oils is greatest when constant temperature) side, the process is merely the quality of the raffinate is highest. If, on the i one of extraction in its usual form. If equilibother hand, successive precipitates are removed rium is approached from the high temperature from the system, the dissolved oil is in equilibrium 20. side, an excess of oil will be dissolved and as the, with the successively lower quality undissolved oil temperature, is lowered to the point at which final and hence the amount of highly parafiinic mateseparation is effected, the excess oil dissolved in rial dissolved at the end of the fractional precipithe solvent layer will be precipitated. The results tation process is reduced considerably. In other in either case will be identical provided sufiicient words, it is possible to obtain a higher yield of time is allowed forequilibrium to be established improved oil of a given quality by fractional pre- 25 between dissolved and undissolved oil. cipitation than by single stage extraction or pre- Resuits comparable to the second case above cipitation, or similarly for a given yield the qualmay be obtainedby dissolving all or a largepority of the improved oil is higher when it is, protion of the'oil'fin one solvent (called solvent A') duced by fractional precipitation than when it and then precipitating a part of said dissolved oil is produced by single stage extraction or precipi- 30 by the addition to the solution of a suitable second tation. solvent (called solvent:v B), or results comparable As specific examples of these methods, assume to the first case above may be-obtained by treating a given oil is dissolved completely in solvent A at the oil with amixture of solvents A and B in the temperature T. vIf the temperature is now re- 5 first instanceduced to T'a definite quantity of oil (Q) will be In oth'er.. words; precipitation may be effected Y precipitated. If this precipitated oil is not reeitlierbyxrediicing the temperature or by the admoved from the system and the temperature. is dition of a suitable second solvent, and in either further reduced to T a second definite quantity case as long as the process is single stage and of oil will be precipitated andthe total quantity 4o equilibrium has been established between "the of undissolved (or precipitated) oil will be Q". 40 solvent layer and the oiljlayer, the results will Comparing this with extraction, let it be assumed be substantially identical, to those obtained by that the same oil is treated with the same ratio simple extraction without precipitation. of .solvent A at the temperature T. Since, the

Fractional precipitation, on the other hand,'is conditions of temperature, solvent, and solvent- -distinctly different from the foregoing. Fracoil ratio are identical, when equilibrium is es- 45 tionalprecipitation is efiected by first dissolving tablished the amount of undissolved oil will be a desired percentage (up to 100 per cent) of the be Q and this oil will'have properties comparaoil in a suitable solvent and then precipitating ble to that of the oil Q in the preceding case. (either by temperature reduction or the addition Similarly, the results obtained by precipitation of asecond solvent, or both) and removlng'sucat temperature T" will be comparable to those 50 cessive amounts of the dissolved oil. In other obtained by extraction at this temperature prowords, each precipitated oil layer is removed prior vided similar conditions obtain. Hence, the reto further preciptation. 1 sults obtained by single stage extraction or by Fractional precipitationis particularly adapted single stage/precipitation will be substantially to the production of several different qualities identicaluhder similar processing conditions. ,55

In the previous conditions of precipitation when the temperature was T and the quantity of oil precipitated was Q the quality and quantity of the oil were independent of the process employed. If, however, the quantity of oil Q is removed when the precipitation temperature is T and the temperature is then reduced to T", a. product Q: will be obtained which will be quite different from the product Q". The product Q: will not only be different from Q" but on the basis of the laws of equilibrium distribution should the products Q: and Q be combined, the properties of such combined products will be different from the properties of Q". These conditions will prevail as long as successive amounts of oil are precipitated.

Fractional precipitation may be effected by reduction in temperature as indicated above or by the addition of successive amounts of a second solvent (solvent B) to a solution of oil dissolved in a first solvent (solvent A) or dissolved in a solvent mixture consisting of solvent B and solvent A. A similar relation exists between single stage extraction, single stage precipitation, and fractional precipitation when oil is precipitated 'by the addition of a second solvent as that which has been indicated previously for the case when oil is precipitated from an oil-solvent solution by reduction in temperature.

In these processes solvent B is so chosen that the solubility of oil in mixtures of solvents A and B is less than the solubility of oil in solvent A at the same temperature.

This invention pertains more particularly to fractional precipitation by the addition of a. second solvent, wherein the solvents are combined efiiciently for this particular purpose. For instance, we find that same particular solvent X may have a greater selectivity than some other solvent Y when fairly low percentage amounts of oil are to be dissolved. However, the selective characteristics of the same two solvents may be reversed when larger percentage amounts of the same oil are to be dissolved so that when fairly high percentage amounts of oil are dissolved solvent Y is more selective than solvent X.

For instance, sulphur dioxide has a higher selectivity than nitrobenzene when low percentage amounts of oil are to be dissolved. On the other hand, when high percentage amounts 01 oil are to be dissolved, nitrobenzene has a higher selectivity than sulphur dioxide.

Similarly the selectivity of pyridine increases with increase in the amount of oil dissolved whereas the selectivity of methyl cellosolve decreases with increasein the amount of oil dissolved. Both of these solvents are excellent solvents for solvent extraction, subject, however, to the limitations set forth.

This invention is directed to the utilization of the foregoing solvents in solvent extraction in a manner to overcome the foregoing limitations making it possible to employ each solvent over a range in percentage of oil dissolved in which said solvent 'is more selective.

This is accomplished by progressively varying the relative concentrations of two solvents of the foregoing characteristics in accordance with the quantity of oil in solution.

This can be can'ied out very eflectively by resorting to fractional precipitation methods employing the solvent whose selectivity increases with the amount of oil in solution to originally dissolve the oil and then employing the solvent whose selectivity increases with decrease in amount of oil dissolved to precipitate oil from solution in said first solvent. I

The fact that the selective rating of a solvent depends not only on the'characteristicsof the solvent but also on the amount of oil dissolved is now fairly well established. We have discovered that it is more eflicient (from the standpoint of economy in degradated oil) to employ different solvents in the extraction of an oil, each solvent being employed over the range in percentage ofoil dissolved in which it is most v I selective. We also find that such a condition can be approached by means of 1 a'process of fractional precipitation in which oil is precipitated by the addition of a second solvent.

As an example of the latter, all or a large part of the oil may be dissolved in solvent Y and successively precipitated by the addition of regulated amounts of solvent X. Since at'the begin-v ning of the step by stepprecipitatlon the solvent mixture is composed chiefly of solvent Y and a large part of the oil is in solution, the selectivity of the mixed solvents is high, since solvent Y predominates. As the step by step precipitation proceeds by the addition of regulated amounts. of solvent X, lesser quantities of oil remain dissolved in the solvent mixture and the influence of solvent X becomes greater and greater such 1 that when a fairly large amount of oil has been precipitated the concentration of solvent X relative to solvent Y is high and the solvent mix-- creases and the concentration of solvent X increases as the step by step precipitation proceeds, it is possible to have an optimum selectivity throughout the process of fractional precipitation.

Although the process of fractional precipitation is applicable to the processing of oils of all types including those from the midcontinent and western fields in which the problem is principally one of deasphaltization to remove prod-.

uctsof extremely lowlubricating value, it is particularly applicable to the processing of petroleum oils of Pennsylvania grade which contain no or at most only minute quantitiespfdeleterious substances and substantiallyall the components of which are suitablefori, lubrication purposes. Thus the problemiin '-i rnproving a Pennsylvania oil for automotive' piirtppiseslis not one of removing substances -which' would be deleterious to an automobilefmotor, such as asphalt, but becomes one of improving the flash and fire points, the reduction inviscositydifference between 100 F. and 210 and the reduction of Conradson carbon residue. For instance, it is found that when working with lubricating stock of Pennsylvania grade since such lubricating stock is already'ot high quality it is possible to produce from the original oil '10 to 15% of very high grade improved oil and yet not seridissolved oil was set aside for tests while the remethylcellosolve was added and the mixture was stirredfonten minutes at F. With constant stirringthe temperature was brought down to 79 F. and the stirring continued atv this temperature for'twenty. minutes. The mixture was then allowed to settle for two hoursat this temand this solvent-free: oil was tested for its various physical properties.

A small amount of the solvent layer containing mainder was used as stock for the next precipitation.

The. next precipitate was formed by adding to the stock a second small amount of methylcellosolve. After stirring the mixture was allowed to settle at the same temperature into a two layer .system as before and the precipitate was removed.

This precedure was repeated seven times. In each step of the fractional precipitation process approximately eight to thirteen per cent of the original oil was precipitated and the total amount precipitated was 71.6 per cent.

Rwults of a similar character are shown in condensed'form in the following table:

methylcellosolve was added with thorough agitation and approximately 7.9 per cent .or the oil was precipitated. This precipitated oil I had a 210 F. viscosity at 249 Saybolt seconds, and A. P. I. gravity of 28.4, and a viscosity index of 111. From these data, it is evident that a'considerably improved product has been obtained.

A second quantity of methylcellosolve (approximately 0.15 volume) was then added'with thorough agitation to the remaining oil dissolved inv the solvent and a second quantity of precipitated all (9.2 per cent of the original oil) was obtained. This fraction had a 210 F. viscosity of 194 Saybolt seconds and an A. P. I. gravity of 28.5 and a viscosity index of 109.

A total of eight different products (see Table I) were obtained from the bright stock by this procedure, seven of thembeing precipitated oils of improved characteristics and one of them .being degradated oil. All of the precipitated oil fractions had physical properties superior to the improved oil was separated.

The above data were obtained for the primary purpose of indicating the improvements which can be made in oils of Pennsylvania grade and do not indicate the maximum efllciency which can be obtained through the utilization of properly designed and operated equipment. The yield 'dex of the precipitates increase from the last Solvent: Pyridine.

.jt Precipitant: .Methylcellosolve. Solvent to oil volume ratioatstart: 6.

The:results 01' our investigation show that by processing a. lubricating stock of Pennsylvania.

grade with selective solvents of the above character and in the above manner, the flash and fire points, the A. P. I..gravity, and the viscosity intoward the first precipitates and the Conradson carbon residue decreases from the last to the first precipitates.

In the example under consideration, the final extract comprised 28.4 per cent of the original oil with a viscosity index of 66, which compares very favorably with lubricating oils from the midcontinent or western fields.

The bright stock of the above table was completely dissolved in six volumes of pyridine at 79 F. Twenty-five hundredths of a volume oi! I TABLE,

Fractional precipitation of bright stock Percent ex- Percent tracted bmied Viscosity Rm 1 7 v gf on- Grav- 01,50 tive Vis- Gravity Color Pour- No. 00111 F E -i 4500: 5.0.1215. 9 A.P.I. at at index F. solvein Origi- Total 20C 120C solvent 1101 in 210 F. F. 1 charge system 01-15 1 bright 100 100 153.0 2452 204 '0.00s0 1.400 00.5

s a 4 Precipitata 7.0 7.0 240.0 4050 20.4 0.0031 1.400 111 a 121, 14-1 4.0 4 1011:.)

2.1 02.1 147.7 2102 20.1 0.0055 1.407 07 104 0.2 10.0 04.4 2050 20.5 0.0025 1.407 100 02.0 00.0 *3 10.1: 15.0 102.2 2105 20.0 0.0010 1.407 100 4 110 00.0 04.2 100.0v 2010 25.0 0.0003. 1.500 02 00 11.5 10.5 141.2 1015 20.0 0.0010 1 407 100 50.0. 01 .5 A4 0.0 10.0 120.0 1002 20.5 0.0021. 1 407- 105 11a 40.5 00.2 144.4 2727 20.7 0.0004 1.505 04 01 10.5 21.7 120.0 1551 20.2 0.0000 1400 104 111 as. 0 7a a 0.0 -25.2 1140 1504 27.0 00051 1.4 100 100 Extract m4 74.0 177.7 4045 20.5 0.0200 .514 00 70 Precipitation temperature: 79 F. of products having'a definite degree of improvement may. beincreased to a large extent dependent upon the. efiiciency of the processing equipment.

Although the highest improvement in viscosity index of the precipitates of Table I is 11.5 points, it is to be pointed outthat the first precipitate had a vascosity at210 F. of 249.3 SayboltUniversal andthat a high degree of improvement was actually efiected.

Oils of equal viscosity index but of different 210 F. viscosity have considerably different relative viscosity-temperature coeflicients than would be anticipated from the numerical value of the viscosity index. As a specific example,

consider the case of an oil having 41210 F. viscosity of 220 seconds S aybolt and a viscosity inoriginal oil and a total yield of 71.6 per cent of dex of l2,5. Oifhand,: it might be assumed that the degree of improvement in this oil is similar to that in an oil having a 210 F. viscosity .of, say, 63 seconds Saybolt and a viscosity index of is only 150 while that ofa 63 second oil is 200.

It is evident that in one case the oil has been improved to within 50 per cent of its theoretical maximum while in the case of the lighter oil the degree of improvement is only 25 per cent of the theoretical maximum.

The theoretical maximum referred to above indicates that degree of improvement in an oil at which the viscosities at 100 F. and 210 F. are equal.

From the foregoing it will be seen that a very considerable improvement has been effected not only in the first precipitate but in many of the succeeding precipitates. I

From the foregoing it will be seen that a mineral oil and particularly one of Pennsylvania grade may be divided into any desired number of portions having different viscosity-temperature coefficients and different viscosities at the same temperature and since both the viscosity and quality of the different fractions vary, it is possible to produce oils of practically any grade and quality by blending the various fractions in any desired proportions. v

It is more difficult to improve a petroleum oil of Pennsylvania grade due to its original high quality and such oils may be very substantially improved by the process herein. The process, however, might be employed to effect improvement in other oils such as those of naphthenic or asphaltic characteristics.

While we have particularly described means for effecting precipitation, it is to be understood that such means might be combined or other means might be employed alone or in conjunction with 'one or more of the means specifically referred to herein. to cause step by step precipitation'by reducing the solvent concentration, for instance, by vaporization of solvent through any means known in the art such as the reduction of the total pressure on the solution with or without the application of heat.

In the claims the'termlubricating oil" when referred to is intended to mean an oil of a viscous character, that is, of the order of 35 Saybolt seconds at 210 F. or above.

. The particular description herein is by way of illustration and it is therefore to be understood that changes, omissions, additions, substitutions, and/or modifications may be made without departing from the spirit of the invention which is intended to be limited only as required by the prior art.

For instance, it is not necessary to remove all of the precipitate formed in each step and a part only thereof might be separated in one or For instance, it is possible more of the steps without departing from the invention.

By a precipitating. solvent is'meant a solvent which when added toa solvent-oil solution forms with the solvent of the solution a solvent mixture of lesser solubility for the oil.

The successive precipitations need not be accomplished by the addition of the same solvent throughout, but a second or a series of solvents may also be employed for this purpose.

The term solvent in its broader significance in cludes any compound or mixture of compounds having desired characteristics whether in the vapor, liquid, and/or solid phase.

We claim:

1. A process comprising dissolving a lubricating oil in pyridine, precipitating oil from said solution in steps by succesively introducing into said solution desired quantities of methylcellosolve, and removing precipitate formed after each addition of methylcellosolve and prior to the next addition of methylcellosolve.

2. A process comprising dissolving a lubricating oil in pyridine, precipitating oil from said solution in steps'by successively introducing into said solution desired quantities of methylcellosolve, removing precipitate formed after each addition of methylcellosolve and prior to the next addition of methylcellosolve, and blending selected precipitated fractions.

3. In a process for extracting a lubricating oil with a mixture of solvents for components of the oil, the steps ofemploying a plurality of selective solvents in said solvent mixture one of which increases in selectivity as the amount of oil in solution increases and another of which increases in selectivity as the amountof oil in solution decreases, forming two, liquid phases of oil and solvent mixture in each of a series of stages in which the amount of oil in solution in said solvent mixture varies progressively from one stage to the next, and increasing the proportion of said second solvent to said first solvent in said solvent mixture as the amount of oil in solution in said solvent mixture decreases and vice versa. 1,

4. In a process for extracting a lubricating oil with. a mixture of solvents for components of the oil, the steps of employing a plurality of selective solvents in said solvent mixture one of which increases in selectivity as the amount of oil in solution increases and another of which increases in selectivity as the amount of oil in solution decreases, forming extract and raffinate phases from said oil and solvent mixture, and increasing the proportion of second solvent to first i'solvent with increase in the proportion of raifinate to extract and vice versa.

WILBERT B. McCLUER.

. MERRELL R. FENSKE. 

